Medical imaging apparatuses are equipment for acquiring an internal structure of an object as an image. Medical image processing apparatuses are noninvasive examination apparatuses that capture images of the structural details of a human body, internal tissue thereof, and fluid flow within a human body, process the images, and show the processed images. A user such as a doctor may diagnose a health state and a disease of a patient by using a medical image output from a medical image processing apparatus.
Representative examples of apparatuses for irradiating radiation onto a patient to scan an object include computed tomography (CT).
CT apparatuses are capable of providing a cross-sectional image of an object and ex-pressing inner structures (e.g., organs such as a kidney, a lung, etc.) of the object without an overlap therebetween, compared to general X-ray apparatuses. Thus, CT apparatuses are widely used for accurately diagnosing a disease. Hereinafter, a medical image acquired by a CT apparatus is referred to as a CT image.
When a CT image is acquired, a CT scan of an object is performed using a CT apparatus to acquire raw data. The CT image is reconstructed using the acquired raw data. Raw data may be projection data acquired by projecting radiation to an object, or a sinogram that is a collection of pieces of projection data.
For example, to acquire a CT image, image reconstruction should be performed using a sinogram acquired by a CT scan. Reconstruction of a CT image will now be described in detail with reference to FIGS. 1 and 2.
FIGS. 1A and 1B are a schematic diagram and a view for describing a CT scan and CT image reconstruction.
In detail, FIG. 1A is a schematic diagram for describing a CT scan that is performed by a CT apparatus that acquires raw data while moving at intervals of a predetermined angle. FIG. 1B illustrates a sinogram acquired by a CT scan and a reconstructed CT image.
A CT apparatus generates X-rays, radiates the X-rays to an object, and detects X-rays having passed through the object by using an X-ray detector (not shown). The X-ray detector produces raw data corresponding to the detected X-rays.
In detail, referring to FIG. 1A, an X-ray generation unit 20 included in the CT apparatus radiates X-rays to an object 25. When the CT apparatus performs a CT scan, the X-ray generation unit 20 rotates around the object 25 and acquires a plurality of pieces of raw data, namely, first, second, and third raw data 30, 31, and 32, corresponding to angles at which the X-ray generation unit 20 has rotated. In detail, the X-ray detector (not shown) detects X-rays applied to the object 25 at a position P1 to thereby acquire the first raw data 30, and detects X-rays applied to the object 25 at a position P2 to thereby acquire the second raw data 31. The X-ray detector (not shown) detects X-rays applied to the object 25 at a position P3 to thereby acquire the third raw data 32. Raw data may be projection data.
Referring to FIG. 1B, a single sinogram 40 may be acquired by combining the first, second, and third raw data 30, 31, and 32 acquired while the X-ray generation unit 20 is rotating at intervals of a predetermined angle as described above with reference to FIG. 1A.
A CT image 50 is reconstructed by back-projection with respect to the sinogram 40.
When the reconstructed CT image 50 has an error, the CT apparatus or an apparatus for processing the reconstructed CT image 50 may correct the error in the reconstructed CT image 50 by acquiring a simulated sinogram via forward-projection with respect to the reconstructed CT image 50 and compensating for a difference between the simulated sinogram and the sinogram 40 acquired by a CT scan.
FIG. 2 illustrates an error existing in a reconstructed CT image.
Referring to FIG. 2, as for a CT image 200 reconstructed using the sinogram 40 acquired by a CT scan, an image error as shown in an internal region 210 of an object may be generated in cases, such as, when insufficient raw data is acquired, when a metal component exists in the object, or when information necessary for reconstruction is insufficient. In detail, the inside of the object may be wrongly expressed as shown in the internal region 210, and a black portion 220 failing to reconstruct an image pixel value may be generated inside the object.
An image error that is generated during this image reconstruction impedes medical image interpretation of a user such as a doctor.
In order for a user such as a doctor to accurately interpret the disease of a patient, a reconstructed CT image should have high accuracy. To obtain an accurate CT image, an error that may be generated in the CT image should be minimized. Accordingly, there is a demand for an apparatus and method of reconstructing a CT image while minimizing generation of an image error.